This invention relates to a rotation transmission device used for selectively transmitting power through a power transmission line.
Conventional rotation transmission devices for selectively transmitting power typically include an inner ring and an outer ring, with cam surfaces and a cylindrical surface formed on one and the other of the outer periphery of the inner ring and the inner periphery of the outer ring, respectively, a plurality of pairs of rollers, each pair being disposed between the cylindrical surface and one of the cam surfaces and circumferentially opposed to each other, and a roller retainer for maintaining the distance between the rollers of each pair of circumferentially opposed rollers. The roller retainer is circumferentially movable between a position where the rollers are wedged between the cam surfaces and the cylindrical surface and a position where the rollers are disengaged from the cam surfaces and the cylindrical surface.
In this rotation transmission device, while the rollers are not wedged between the cam surfaces and the cylindrical surface, rotation is not transmitted between the inner and outer rings. When the rollers are wedged between the cam surfaces and the cylindrical surface, rotation is transmitted between the inner and outer rings. In order to change the direction of rotation to be transmitted between the inner and outer rings, it is necessary to circumferentially move the roller retainer from the position where the rollers are wedged in one rotational direction to the position where the rollers are wedged in the opposite rotational direction, relative to one of the inner and outer rings that is formed with the cam surfaces.
In order to improve the response of such changes in the direction of rotation, JP patent publication 2003-262238A proposes to circumferentially arrange either the cam surfaces or the rollers with equal pitches and the others with unequal pitches. With this arrangement, because rollers that are wedged when transmitting rotation in one direction are different from rollers that are wedged when transmitting rotation in the opposite direction, it is possible to minimize the distance by which the roller retainer has to be circumferentially moved to change the direction of rotation, thereby improving the response of such changes in direction of rotation.
But with this rotation transmission device, in order to change the direction in which rotation is transmitted between the inner and outer rings, it is necessary to circumferentially move the roller retainer from the position where the rollers are wedged in one rotational direction to the position where the rollers are wedges in the opposite rotational direction. Thus, a delay in response necessarily occurs because the roller retainer has to be moved to change the direction of rotation. Thus, it may be difficult to sufficiently quickly change the direction of rotation. If the distance by which the roller retainer has to be moved to change the direction of rotation is reduced in an attempt to improve the response of changes in the direction of rotation, the rollers are more likely to be untimely wedged between the cam surfaces and the cylindrical surface, so that the reliability in operation deteriorates.
An object of this invention is to provide a rotation transmission device which can more quickly change the direction of rotation.